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The University of Southampton
Chemistry

Research project: Rios: Design of new catalysts

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The design of new methodologies for the synthesis of complex scaffolds often requires the development of new catalyst that fulfills some of the limitations of the existent catalysts.

In our research group, we have the aim to design new catalysts or catalytic systems that lead to improved reaction conditions, stereoselectivities or new reactivities.

In 2009 we developed a catalytic system consisting in the addition of a thiourea co-catalyst to a proline catalyzed Aldol reaction. We determined that the addition of thiourea allow a faster and easier formation of the enamine in apolar solvents probably though the Hydrogen bond interactions between the thiourea co-catalyst and the carboxylate of proline. Proline is insoluble in apolar solvents like toluene. However, the use of thioureas as co-catalyst solubilizes the proline making a most powerful catalyst (Figure 1; right vial).1

Effect of the addition of thiourea cocatalyst

Figure: effect of the addition of thiourea cocatalyst in the solubility of proline in toluene/acetone 5:1: first vial thiourea, second vial proline, third vial proline + thiourea (all is soluble).

We tested this new catalytic system in the desymmetrization of 4-substituted-cyclohexanones by an aldol reaction, affording the final compounds in excellent yields and stereoselectivities.2

 

 

Aldol desymmetrization reaction




 

 

 

Figure: Aldol desymmetrization reaction

 

Related Papers:

1 “Substrate-dependent nonlinear effects in proline-thiourea catalyzed aldol reactions. Unraveling the role of the thiourea co-catalyst”. N. El-Hamdouni, X. Companyó, R. Rios*, A. Moyano*. Chem. Eur. J. 2010, 16, 1142-1148.

2 “Highly Enantio- and Diastereoselective Organocatalytic Desymmetrization of Prochiral Cyclohexanones by Simple Direct Aldol Reaction Catalyzed by Proline”. X. Companyó, G. Valero, L. Crovetto, A. Moyano, R. Rios. Chem. Eur. J. 2009, 15, 6556-6558.

 

Related research groups

Organic Chemistry: Synthesis, Catalysis and Flow
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